Apparatus and method for forming organic thin film transistor

ABSTRACT

A method for forming an organic thin film transistor is provided. An organic semiconductor layer, a source electrode, a drain electrode, a gate electrode, and an insulating layer are formed on an insulating substrate. A method for forming the organic semiconductor layer is provided. An evaporating source is provided, and the evaporating source and the insulating substrate are spaced from each other. The carbon nanotube film structure is heated to gasify the organic semiconductor material to form the organic semiconductor layer on a depositing surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Chinese Patent Application No.201610384814.9, filed on Jun. 2, 2016, the disclosure of which isincorporated herein by reference.

FIELD

The present disclosure relates to an apparatus and a method for formingan organic thin film transistor.

BACKGROUND

An organic thin film transistor (OTFT) has been used in electronicpapers, sensors, memories, flexible displays and integrated circuitsbecause of having a light weight, flexibility, and a low manufacturingcost. An organic semiconductor layer can be formed on a surface of aninsulating substrate by spin coating and etching. Conventionally, theorganic semiconductor layer may be formed by a vapor deposition method.However, in order to form a uniform organic semiconductor layer, it isnecessary to form a uniform gaseous evaporating material around adepositing substrate. Since it is difficult to control a diffusiondirection of atoms of the gaseous evaporating material, most of theevaporating material can not be attached to a surface of the depositingsubstrate, and a deposition rate of the evaporating material is slow.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present technology will now be described, by wayof example only, with reference to the attached figures.

FIG. 1 is a flowchart of one embodiment of a method for forming anorganic semiconductor layer.

FIG. 2 is a side view of one embodiment of an apparatus for forming anorganic thin film transistor.

FIG. 3 is a side view of one embodiment of the organic thin filmtransistor.

FIG. 4 is a scanning electron microscope (SEM) image of a carbonnanotube film drawn from a carbon nanotube array.

FIG. 5 is a SEM image of a carbon nanotube film structure.

FIG. 6 is a side view of another embodiment of an apparatus for formingan organic thin film transistor.

FIG. 7 is a SEM of one embodiment of the evaporating source afterevaporation.

FIG. 8 is a side view of another embodiment of an apparatus for formingthe organic thin film transistor.

FIG. 9 is a side view of another embodiment of the organic thin filmtransistor.

DETAILED DESCRIPTION

The disclosure is illustrated by way of example and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “an” or “one” embodiment in this disclosure are not necessarily tothe same embodiment, and such references mean “at least one”.

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures, and components havenot been described in detail so as not to obscure the related relevantfeature being described. Also, the description is not to be consideredas limiting the scope of the embodiments described herein. The drawingsare not necessarily to scale, and the proportions of certain parts maybe exaggerated to illustrate details and features of the presentdisclosure better.

Several definitions that apply throughout this disclosure will now bepresented.

The term “comprise” or “comprising” when utilized, means “include orincluding, but not necessarily limited to”; it specifically indicatesopen-ended inclusion or membership in the so-described combination,group, series, and the like.

Referring to FIG. 1 to FIG. 3, in one embodiment, a method of forming anorganic thin film transistor 200 is provided. An organic semiconductorlayer 230, a source electrode 220, a drain electrode 240, a gateelectrode 250, and an insulating layer 260 is formed on a insulatingsubstrate 210. A method for forming the organic semiconductor layer 230comprises the steps of:

(S1) Providing an evaporating source 110, wherein the evaporating source110 comprises a carbon nanotube film structure 112 and an organicsemiconductor material 114, and the organic semiconductor material 114is located on a surface of the carbon nanotube film structure 112.

(S2) Spacing the evaporating source 110 from the insulating substrate210, and inputting an electromagnetic signal or an electrical signal toheat the carbon nanotube film structure 112 to gasify the organicsemiconductor material 114 and form the organic semiconductor layer 230on a depositing surface.

The insulating substrate 210 can be a hard substrate or a flexiblesubstrate. In one embodiment, the organic semiconductor material 114 isa material of the organic semiconductor layer 230. In anotherembodiment, the organic semiconductor material 114 is a precursor forforming the organic semiconductor layer 230, and the precursor reacts toform the material of the organic semiconductor layer 230 during vapordeposition.

The material of the organic semiconductor layer 230 may be tetracene,pentacene, hexacene, rubrene, anthracene, α-Sexithiophene(α-6T),poly-3-hexylthiophene(P3HT), polypyrrole, poly thiophene, polyphenol,poly 2,5 thiophene acetylene, copper phthalocyanine, nickelphthalocyanine, zinc phthalocyanine, free phthalocyanine, fluorinatedphthalocyanine copper, fluorinated phthalocyanine chromium, fluorinatedphthalocyanine zinc, free fluorinated phthalocyanine orpolybenzimidazole benzophenanthroline(BBL). The organic semiconductormaterial 114 and the material of the organic semiconductor layer 230 arenot limited to the above materials, as long as a gasificationtemperature of the organic semiconductor material 114 is lower than agasification temperature of carbon nanotubes under the same conditions,and the organic semiconductor material 114 does not react with carbonduring the vapor deposition process. In one embodiment, the gasificationtemperature of the organic semiconductor material 114 is lower than orequal to 300° C.

The carbon nanotube film structure 112 is a carrying structure for theorganic semiconductor material 114. The organic semiconductor material114 is located on a surface of the carbon nanotube film structure 112.The carbon nanotube film structure 112 is configured to form afree-standing structure and can be suspended by supporters. The organicsemiconductor material 114 is located on a suspended surface of carbonnanotube film structure 112. In one embodiment, in S1, two supporters120 are provided. The two supporters 120 are spaced from each other anddisposed on opposite two ends of the carbon nanotube film structure 112.The carbon nanotube film structure 112 is suspended by the twosupporters 120.

The carbon nanotube film structure 112 comprises a single carbonnanotube film, or at least two stacked carbon nanotube films. The carbonnanotube film comprises a plurality of nanotubes. The plurality ofnanotubes are generally parallel to each other, and arrangedsubstantially parallel to a surface of the carbon nanotube filmstructure 112. The carbon nanotube film structure 112 has uniformthickness. The carbon nanotube film can be regarded as a macro membranestructure. In the macro membrane structure, an end of one carbonnanotube is joined to another end of an adjacent carbon nanotubearranged substantially along the same direction by Van der Waalsattractive force. The carbon nanotube film structure 112 and the carbonnanotube film have a macro area and a microscopic area. The macro areadenotes a membrane area of the carbon nanotube film structure 112 or thecarbon nanotube film when the carbon nanotube film structure 112 or thecarbon nanotube film is regarded as a membrane structure. In terms of amicroscopic area, the carbon nanotube film structure 112 or the carbonnanotube film is a network structure having a large number of nanotubesjoined end to end. The microscopic area signifies a surface area of thecarbon nanotubes actually carrying the organic semiconductor material114.

In one embodiment, the carbon nanotube film is formed by drawing from acarbon nanotube array. This carbon nanotube array is grown on a growthsurface of a substrate by chemical vapor deposition method. The carbonnanotubes in the carbon nanotube array are substantially parallel toeach other and perpendicular to the growth surface of the substrate.Adjacent carbon nanotubes make mutual contact and combine by van derWaals forces. By controlling the growth conditions, the carbon nanotubearray is substantially free of impurities such as amorphous carbon orresidual catalyst metal particles. The carbon nanotube array beingsubstantially free of impurities with carbon nanotubes in close contactwith each other, there is a larger van der Waals forces between adjacentcarbon nanotubes. When carbon nanotube fragments (CNT fragments) aredrawn, adjacent carbon nanotubes are continuously drawn out end to endby van der Waals forces to form a free-standing and uninterruptedmacroscopic carbon nanotube film. The carbon nanotube array made ofcarbon nanotubes drawn end to end is also known as a super-alignedcarbon nanotube array. In order to grow the super-aligned carbonnanotube array, the growth substrate material can be a P-type silicon,an N-type silicon, or a silicon oxide substrate.

The carbon nanotube film includes a plurality of carbon nanotubes thatcan be joined end to end and arranged substantially along the samedirection. Referring to FIG. 4, a majority of carbon nanotubes in thecarbon nanotube film can be oriented along a preferred orientation,meaning that a large number of the carbon nanotubes in the carbonnanotube film are arranged substantially along the same direction. Anend of one carbon nanotube is joined to another end of an adjacentcarbon nanotube arranged substantially along the same direction by Vander Waals attractive force. A small number of the carbon nanotubes arerandomly arranged in the carbon nanotube film, and has a small if notnegligible effect on the larger number of the carbon nanotubes in thecarbon nanotube film arranged substantially along the same direction.

More specifically, the carbon nanotube drawn film includes a pluralityof successively oriented carbon nanotube segments joined end-to-end byVan der Waals attractive force therebetween. Each carbon nanotubesegment includes a plurality of carbon nanotubes substantially parallelto each other and joined by Van der Waals attractive force therebetween.The carbon nanotube segments can vary in width, thickness, uniformity,and shape. The carbon nanotubes in the carbon nanotube drawn film arealso substantially oriented along a preferred orientation.

Microscopically, the carbon nanotubes oriented substantially along thesame direction may not be perfectly aligned in a straight line, and somecurve portions may exist. It can be understood that some carbonnanotubes located substantially side by side and oriented along the samedirection in contact with each other cannot be excluded. The carbonnanotube film includes a plurality of gaps between the adjacent carbonnanotubes so that the carbon nanotube film can have better transparencyand higher specific surface area.

The carbon nanotube film is capable of forming a free-standingstructure. The term “free-standing structure” can be defined as astructure that does not require a substrate for support. For example, afree standing structure can sustain the weight of itself when it ishoisted by a portion thereof without any damage to its structuralintegrity. So, if the carbon nanotube drawn film is placed between twoseparate supporters, a portion of the carbon nanotube drawn film, not incontact with the two supporters, would be suspended between the twosupporters and yet maintain film structural integrity. The free-standingstructure of the carbon nanotube drawn film is realized by thesuccessive carbon nanotubes joined end to end by Van der Waalsattractive force.

The carbon nanotube film has a small and uniform thickness in a rangefrom about 0.5 nm to 10 microns. Since the carbon nanotube film drawnfrom the carbon nanotube array can form the free-standing structure onlyby van der Waals forces between the carbon nanotubes, the carbonnanotube film has a large specific surface area. In one embodiment, thespecific surface area of the carbon nanotube film measured by the BETmethod is in a range from about 200 m²/g to 2600 m²/g. A mass per unitarea of the carbon nanotube film is in a range from about 0.01 g/m² toabout 0.1 g/m² (area here refers to the macro area of the carbonnanotube film). In another embodiment, the mass per unit area of thecarbon nanotube film is about 0.05 g/m². Since the carbon nanotube filmhas a minimal thickness and the heat capacity of the carbon nanotube isitself small, the carbon nanotube film has small heat capacity per unitarea. In one embodiment, the heat capacity per unit area of the carbonnanotube film is less than 2×10⁻⁴ J/cm²·K.

The carbon nanotube film structure 112 may includes at least two stackedcarbon nanotube films. In one embodiment, a number of layers of thestacked carbon nanotube film is 50 layers or less. In anotherembodiment, the number of layers of the stacked carbon nanotube film is10 layers or less. Additionally, an angle can exist between theorientation of carbon nanotubes in adjacent carbon nanotube films.Adjacent carbon nanotube films can be combined by only Van der Waalsattractive forces therebetween without the need of an adhesive. An anglebetween the aligned directions of the carbon nanotubes in two adjacentcarbon nanotube films can range from about 0 degrees to about 90degrees. In one embodiment, referring to FIG. 5, the carbon nanotubefilm structure 112 includes at least two stacked carbon nanotube films,and the angle between the aligned directions of the carbon nanotubes inthe two adjacent carbon nanotube films is 90 degrees.

The organic semiconductor material 114 is disposed on the surface of thecarbon nanotube film structure 112 by a plurality of methods, such assolution method, vapor deposition method, plating method or chemicalplating method. The deposition method may be chemical vapor deposition(CVD) method or physical vapor deposition (PVD) method.

A solution method for disposing the organic semiconductor material 114on the surface of the carbon nanotube film structure 112 comprises thesteps of: (11) dissolving or uniformly dispersing the organicsemiconductor material 114 in a solvent to form a mixture; (12)uniformly attaching the mixture to the carbon nanotube film structure112 by spray coating method, spin coating method, or dip coating method;(13) evaporating and drying the solvent to make the organicsemiconductor material 114 uniformly attach on the surface of the carbonnanotube film structure 112. In the (11), the mixture can be a solutionor a dispersion.

When the organic semiconductor material 114 includes a plurality ofmaterials, the plurality of materials can be dissolved in a liquid phasesolvent and mixed with a required ratio in advance so that the pluralityof materials can be disposed on different locations of the carbonnanotube film structure 112 by the required ratio.

The step (12) and the step (13) may be repeated a plurality of times sothat the organic semiconductor material 114 can have a required amounton the surface of the carbon nanotube film structure 112.

The organic semiconductor material 114 is adhered on and coats thesurface of the carbon nanotube film structure 112. Macroscopically, theorganic semiconductor material 114 can be seen as a layer formed on atleast one surface of the carbon nanotube film structure 112. In oneembodiment, the organic semiconductor material 114 is coated on twosurfaces of the carbon nanotube film structure 112. The organicsemiconductor material 114 and the carbon nanotube film structure 112form a composite membrane. In one embodiment, a thickness of thecomposite membrane is 100 microns or less. In another embodiment, thethickness of the composite membrane is 5 microns or less. An amount ofthe organic semiconductor material 114 carried per unit area of thecarbon nanotube film structure 112 is small. Thus, in microscopic terms,a morphology of the organic semiconductor material 114 may be nanoscaleparticles or layers with nanoscale thickness, being attached to a singlecarbon nanotube surface or the surfaces of a few carbon nanotubes. Inone embodiment, the morphology of the organic semiconductor material 114is particles. A diameter of the particles is in a range from about 1nanometer to 500 nanometers. In another embodiment, the morphology ofthe organic semiconductor material 114 is a layer. A thickness of theorganic semiconductor material 114 is in a range from about 1 nanometerto 500 nanometers. The organic semiconductor material 114 can completelycover and coat a single carbon nanotube for all or part of its length.The morphology of the organic semiconductor material 114 coated on thesurface of the carbon nanotube film structure 112 is associated with theamount of the organic semiconductor material 114, species of the organicsemiconductor material 114, a wetting performance of the carbonnanotubes, and other properties. For example, the organic semiconductormaterial 114 is more likely to be particle when the organicsemiconductor material 114 is not soaked in the surface of the carbonnanotube. The organic semiconductor material 114 is more likely touniformly coat a single carbon nanotube surface to form a continuouslayer when the organic semiconductor material 114 is soaked in thesurface of carbon nanotubes. In addition, when the organic semiconductormaterial 114 is an organic material having high viscosity, it may form acontinuous film on the surface of the carbon nanotube film structure112. No matter what the morphology of the organic semiconductor material114 may be, the amount of the organic semiconductor material 114 carriedby per unit area of the carbon nanotube film structure 112 is small.Thus, the electromagnetic signal or the electrical signal caninstantaneously and completely gasify the organic semiconductor material114. In one embodiment, the organic semiconductor material 114 iscompletely gasified within 1 second. In another embodiment, the organicsemiconductor material 114 is completely gasified within 10microseconds. The organic semiconductor material 114 is uniformlydisposed on the surface of the carbon nanotube film structure 112, sothat different locations of the carbon nanotube film structure 112 carrysubstantially equal amounts of the organic semiconductor material 114.

In the S2, the evaporating source 110 is spaced from the insulatingsubstrate 210. A distance between the insulating substrate 210 and thecarbon nanotube film structure 112 is substantially equal. The carbonnanotube film structure 112 is substantially parallel to the depositingsurface. In one embodiment, the carbon nanotube film structure 112coated with the organic semiconductor material 114 is spaced from andfaces to the depositing surface, and a distance between the carbonnanotube film structure 112 and the depositing surface is in a rangefrom about 1 micrometer to about 10 millimeters. The area of thedepositing surface is equal or less than the macro area of the carbonnanotube film structure 112. Thus, a gaseous organic semiconductormaterial can reach the depositing surface substantially at the sametime. The depositing surface can be a surface of the insulatingsubstrate 210 or a surface of the insulating layer 260.

The S2 can be carried out in atmosphere or in vacuum. In one embodiment,the evaporating source 110 is located in a vacuum room 130. Theelectromagnetic signal or the electrical signal is inputted to thecarbon nanotube film structure 112 to evaporate the organicsemiconductor material 114 and form the organic semiconductor layer 230on the depositing surface.

When the electromagnetic signal or the electrical signal is inputted toheat the carbon nanotube film structure 112, the organic semiconductormaterial 114 is rapidly heated to a evaporation or sublimationtemperature. Since per unit area of the carbon nanotube film structure112 carries a small amount of the organic semiconductor material 114,all the organic semiconductor material 114 may instantly gasify. Thecarbon nanotube film structure 112 and the depositing surface areparallel to and spaced from each other. In one embodiment, the distancebetween the depositing surface and the carbon nanotube film structure112 is in a range from about 1 micrometer to about 10 millimeters. Sincethe distance between the carbon nanotube film structure 112 and thedepositing surface is small, the gaseous organic semiconductor materialevaporated from the carbon nanotube film structure 112 is rapidlyattached to the depositing surface to form the organic semiconductorlayer 230. The area of the depositing surface is equal or less than themacro area of the carbon nanotube film structure 112. The carbonnanotube film structure 112 can completely cover the depositing surface.Thus, the organic semiconductor material 114 is evaporated to thedepositing surface as a correspondence to the carbon nanotube filmstructure 112 to form the organic semiconductor layer 230. Since theorganic semiconductor material 114 is uniformly carried by the carbonnanotube film structure 112, the organic semiconductor layer 230 is alsoa uniform structure. When the organic semiconductor material 114comprises the plurality of materials, a proportion of the plurality ofmaterials is same in different locations of the carbon nanotube filmstructure 112. Thus, the plurality of materials still has sameproportion in the gaseous organic semiconductor material, and a uniformorganic semiconductor layer 230 can be formed on the depositing surface.

The electromagnetic signal can be inputted to the carbon nanotube filmstructure 112 by an electromagnetic signal input device 140. Theelectromagnetic signal input device 140 may be located in the vacuumroom 130 or outside the vacuum room 130 as long as an emittedelectromagnetic signal can be transmitted to the carbon nanotube filmstructure 112. An average power density of the electromagnetic signal isin a range from about 100 mW/mm² to 20 W/mm². Since the structure of thecarbon nanotube film structure 112 has a large specific surface area,the carbon nanotube film structure 112 can quickly exchange heat withsurrounding medium, and heat signals generated by the carbon nanotubefilm structure 112 can quickly heat the organic semiconductor material114. Since the amount of the organic semiconductor material 114 disposedon per unit macro area of the carbon nanotube film structure 112 issmall, the organic semiconductor material 114 can be completely gasifiedinstantly by the heat signals.

Referring FIG. 6, the electrical signal can be inputted to the carbonnanotube film structure 112 by a first electrical signal input electrode150 and a second electrical signal input electrode 152. The firstelectrical signal input electrode 150 and the second electrical signalinput electrode 152 are spaced from each other and electricallyconnected to the carbon nanotube film structure 112. In one embodiment,the carbon nanotube film structure 112 is suspended by the firstelectrical signal input electrode 150 and the second electrical signalinput electrode 152. The carbon nanotube film structure 112 is aresistive element. The carbon nanotube film structure 112 has the smallheat capacity per unit area, and has the large specific surface area buta minimal thickness. In one embodiment, the heat capacity per unit areaof the carbon nanotube film structure 112 is less than 2×10⁻⁴ J/cm²·K.In another embodiment, the heat capacity per unit area of the carbonnanotube film structure 112 is less than 1.7×10⁻⁶ J/cm²·K. The specificsurface area of the carbon nanotube film structure 112 is larger than200 m²/g. The thickness of the carbon nanotube film structure 112 isless than 100 micrometers. The first electrical signal input electrode150 and the second electrical signal input electrode 152 input theelectrical signal to the carbon nanotube film structure 112. Since thecarbon nanotube film structure 112 has the small heat capacity per unitarea, the carbon nanotube film structure 112 can convert electricalenergy to heat quickly, and a temperature of the carbon nanotube filmstructure 112 can rise rapidly. Since the carbon nanotube film structure112 has the large specific surface area and is very thin, the carbonnanotube film structure 112 can rapidly transfer heat to the organicsemiconductor material 114. The organic semiconductor material 114 israpidly heated to the evaporation or sublimation temperature.

The first electrical signal input electrode 150 and the secondelectrical signal input electrode 152 are electrically connected to thecarbon nanotube film structure 112. In one embodiment, the firstelectrical signal input electrode 150 and the second electrical signalinput electrode 152 are directly disposed on the surface of the carbonnanotube film structure 112. The first electrical signal input electrode150 and the second electrical signal input electrode 152 can input acurrent to the carbon nanotube film structure 112. The first electricalsignal input electrode 150 and the second electrical signal inputelectrode 152 are spaced from each other and disposed at either end ofthe carbon nanotube film structure 112.

In one embodiment, the plurality of carbon nanotubes in the carbonnanotube film structure 112 extends from the first electrical signalinput electrode 150 to the second electrical signal input electrode 152.When the carbon nanotube film structure 112 consists of one carbonnanotube film, or of at least two films stacked along a same direction(i.e., the carbon nanotubes in different carbon nanotube films beingarranged in a same direction and parallel to each other), the pluralityof carbon nanotubes of the carbon nanotube film structure 112 extendfrom the first electrical signal input electrode 150 to the secondelectrical signal input electrode 152. In one embodiment, the firstelectrical signal input electrode 150 and the second electrical signalinput electrode 152 are linear structures and are perpendicular toextended directions of the carbon nanotubes of at least one carbonnanotube film in the carbon nanotube film structure 112. In oneembodiment, the first electrical signal input electrode 150 and thesecond electrical signal input electrode 152 are same as a length of thecarbon nanotube film structure 112, the first electrical signal inputelectrode 150 and the second electrical signal input electrode 152 thusextending from one end of the carbon nanotube film structure 112 to theother end. Thus, each of the first electrical signal input electrode 150and the second electrical signal input electrode 152 is connected to twoends of the carbon nanotube film structure 112.

The carbon nanotube film structure 112 is the free-standing structureand can be suspended by the first electrical signal input electrode 150and the second electrical signal input electrode 152. In one embodiment,the first electrical signal input electrode 150 and the secondelectrical signal input electrode 152 have sufficient strength tosupport the carbon nanotube film structure 112, and two supporters 120may be omitted. The first electrical signal input electrode 150 and thesecond electrical signal input electrode 152 may be conductive wires orconductive rods.

In the S2, the electrical signal is inputted to the carbon nanotube filmstructure 112 through the first electrical signal input electrode 150and the second electrical signal input electrode 152. When the electricsignal is a direct current signal, the first electrical signal inputelectrode 150 and the second electrical signal input electrode 152 arerespectively electrically connected to a positive and a negative of adirect current source. The direct current power inputs a direct currentsignal to the carbon nanotube film structure 112 through the firstelectrical signal input electrode 150 and the second electrical signalinput electrode 152. When the electrical signal is an alternatingcurrent signal, the first electrical signal input electrode 150 iselectrically connected to an alternating current source, and the secondelectrical signal input electrode 152 is connected to earth. Thetemperature of the carbon nanotube film structure 112 can reach thegasification temperature of the organic semiconductor material 114 byinputting an electrical signal power to the evaporating source 110. Theelectrical signal power can be calculated according to the formula σT⁴S.Wherein σ represents Stefan-Boltzmann constant; T represents thegasification temperature of the organic semiconductor material 114; andS represents the macro area of the carbon nanotube film structure 112.The larger the macro area of the carbon nanotube film structure 112 andthe higher the gasification temperature of the organic semiconductormaterial 114, the greater the electrical signal power. Since the carbonnanotube film structure 112 has the small heat capacity per unit area,the carbon nanotube film structure 112 can quickly generate thermalresponse to raise the temperature. Since the carbon nanotube filmstructure 112 has the large specific surface area, the carbon nanotubefilm structure 112 can quickly exchange heat with surrounding medium,and heat signals generated by the carbon nanotube film structure 112 canquickly heat the organic semiconductor material 114. Since the amount ofthe organic semiconductor material 114 disposed on per unit macro areaof the carbon nanotube film structure 112 is small, the organicsemiconductor material 114 can be completely gasified instantly by theheat signals.

FIG. 7 shows a structure of the evaporating source 110 after vacuumevaporation. After evaporating the organic semiconductor material 114disposed on the surface structure of the carbon nanotube film structure112, the carbon nanotube film structure 112 retains an original networkstructure, and the carbon nanotubes of the carbon nanotube filmstructure 112 are still joined end to end.

Referring FIG. 8, in one embodiment, the S2 further comprises a step ofproviding a patterned grid 160 and locating the patterned grid 160between the evaporating source 110 and the depositing surface to form apatterned organic semiconductor layer 230.

The patterned grid 160 comprises at least one through hole. The throughhole may have a required shape and size. In one embodiment, thepatterned grid 160 is respectively in direct contact with the depositingsurface and the carbon nanotube film structure 112. In anotherembodiment, the patterned grid 160 is respectively spaced from thedepositing surface and the carbon nanotube film structure 112. Thepatterned grid 160 is respectively parallel to the depositing surfaceand the carbon nanotube film structure 112. The gaseous organicsemiconductor material is instantly adhered to the depositing surface toform the patterned organic semiconductor layer 230 after passing throughthe at least one through hole. A pattern of the patterned organicsemiconductor layer 230 is corresponding to the required shape and sizeof the through hole of the patterned grid 160. In one embodiment, thepatterned grid 160 comprises an array of through holes, thus an array oforganic semiconductor layers 230 can be formed on the depositing surfaceto form a TFT array.

The organic thin film transistor 200 is located on the surface of theinsulating substrate 210. The organic thin film transistor 200 comprisesthe organic semiconductor layer 230, the source electrode 220, the drainelectrode 240, the gate electrode 250, and the insulating layer 260. Thesource electrode 220 is spaced from the drain electrode 240. The organicsemiconductor layer 230 is electrically connected to the sourceelectrode 220 and the drain electrode 240. The gate electrode 250 isinsulated from the organic semiconductor layer 230, the source electrode220, and the drain electrode 240 by the insulating layer 260. Theorganic thin film transistor 200 may be a top gate type or a back gatetype.

Referring to FIG. 3, when the organic thin film transistor 200 is thetop gate type, the organic semiconductor layer 230 is located on asurface of the insulating substrate 210. The source electrode 220 andthe drain electrode 240 are located on a surface of the organicsemiconductor layer 230. The insulating layer 260 is located on thesurface of the organic semiconductor layer 230. The gate electrode 250is located on a surface of the insulating layer 260 and is insulatedfrom the organic semiconductor layer 230, the source electrode 220, andthe drain electrode 240 through the insulating layer 260. The organicsemiconductor layer 230 is located in a region between the sourceelectrode 220 and the drain electrode 240 to form a channel.

The location of the source electrode 220 and the drain electrode 240 arenot limited, as long as the source electrode 220 and the drain electrode240 are spaced apart from each other and electrically connected to theorganic semiconductor layer 230. In one embodiment, the source electrode220 and the drain electrode 240 is disposed between the insulating layer260 and the organic semiconductor layer 230. The source electrode 220,the drain electrode 240 and the gate electrode 250 are located on a sameside of the organic semiconductor layer 230 to form a coplanar organicthin film transistor 200. In another embodiment, the source electrode220 and the drain electrode 240 is disposed between the insulatingsubstrate 210 and the organic semiconductor layer 230. The sourceelectrode 220, the drain electrode 240 and the gate electrode 250 arelocated on different sides of the organic semiconductor layer 230 toform a staggered organic thin film transistor 200.

In one embodiment, a method for forming the coplanar organic thin filmtransistor 200 is provided. The depositing surface in this method is asurface of the insulating substrate 210. The method for forming thecoplanar organic thin film transistor 200 comprises the following steps:

-   -   T1: forming the organic semiconductor layer 230 on the        insulating substrate 210, comprising:        -   T11: providing the evaporating source 110, wherein the            evaporating source 110 comprises the carbon nanotube film            structure 112 and the organic semiconductor layer material            114, and the organic semiconductor layer material 114 is            located on the surface of the carbon nanotube film structure            112; and        -   T12: spacing the evaporating source 110 from the insulating            substrate 210, and inputting the electromagnetic signal or            the electrical signal to the carbon nanotube film structure            112 to gasify the organic semiconductor material 114 and            form the organic semiconductor layer 230 on the insulating            substrate 210;    -   T2: forming the source electrode 220 and the drain electrode 240        on the organic semiconductor layer 230, wherein the source        electrode 220 and the drain electrode 240 are spaced from each        other and electrically connected to the organic semiconductor        layer 230;    -   T3: forming the insulating layer 260 to cover the source        electrode 220, the drain electrode 240, and the organic        semiconductor layer 230; and    -   T4: forming the gate electrode 250 on the insulating layer 260.

In another embodiment, a method for forming the staggered organic thinfilm transistor 200 is provided. The depositing surface in this methodcomprises the surface of the insulating substrate 210, a surface of thesource electrode 220, and a surface of the drain electrode 240. In oneembodiment, the depositing surface consists of the surface of theinsulating substrate 210, the surface of the source electrode 220, andthe surface of the drain electrode 240. The method for forming thestaggered organic thin film transistor 200 comprises the followingsteps:

-   -   N1: forming the source electrode 220 and the drain electrode 240        on the surface of the insulating substrate 210, wherein the        source electrode 220 and the drain electrode 240 are spaced from        each other;    -   N2: forming the organic semiconductor layer 230 on the        insulating substrate 210, comprising:        -   N21: providing the evaporating source 110, wherein the            evaporating source 110 comprises the carbon nanotube film            structure 112 and the organic semiconductor material 114,            and the organic semiconductor material 114 is located on the            surface of the carbon nanotube film structure 112; and        -   N22: spacing the evaporating source 110 from the insulating            substrate 210, the source electrode 220 and the drain            electrode 240, and inputting the electromagnetic signal or            the electrical signal to the carbon nanotube film structure            112 to gasify the organic semiconductor material 114 and            form the organic semiconductor layer 230 on the insulating            substrate 210, wherein the source electrode 220 and the            drain electrode 240 are covered by the organic semiconductor            layer 230 and electrically connected to the organic            semiconductor layer 230;    -   N3: forming the insulating layer 260 to cover the source        electrode 220, the drain electrode 240, and the organic        semiconductor layer 230; and    -   N4: forming the gate electrode 250 on the insulating layer 260.

Referring to FIG. 9, in one embodiment, the organic thin film transistor200 is a back gate type. The gate electrode 250 is disposed on thesurface of the insulating substrate 210. The insulating layer 260 isdisposed on the surface of the gate electrode 250. The organicsemiconductor layer 230 is disposed on the surface of the insulatinglayer 260 and is insulated from the gate electrode 250 by the insulatinglayer 260. The source electrode 220 and the drain electrode 240 arespaced from each other and electrically connected to the organicsemiconductor layer 230. The source electrode 220, the drain electrode240, and the organic semiconductor layer 230 are electrically insulatedfrom the gate electrode 250 through the insulating layer 260. Theorganic semiconductor layer 230 is located in a region between thesource electrode 220 and the drain electrode 240 to form a channel.

In one embodiment, the source electrode 220 and the drain electrode 240are spaced apart from each other and disposed on the organicsemiconductor layer 230. The source electrode 220, the drain electrode240 and the gate electrode 250 are located on different sides of theorganic semiconductor layer 230 to form a reverse staggered organic thinfilm transistor 200. In another embodiment, the source electrode 220 andthe drain electrode 240 are spaced apart from each other and disposedbetween the insulating layer 260 and the organic semiconductor layer230. The source electrode 220, the drain electrode 240 and the gateelectrode 250 are formed on a same side of the organic semiconductorlayer 230 to form a reverse coplanar type organic thin film transistor200.

In one embodiment, a method for forming the reverse coplanar organicthin film transistor 200 is provided. The depositing surface in thismethod consists of a surface of the insulating layer 260, the surface ofthe source electrode 220, and the surface of the drain electrode 240.The method for forming the reverse coplanar organic thin film transistor200 comprises the following steps:

-   -   M1: forming the gate electrode 250 on the surface the insulating        substrate 210;    -   M2: forming the insulating layer 260 to cover the gate electrode        250;    -   M3: forming the source electrode 220 and the drain electrode 240        on the insulating layer 260, wherein the source electrode 220        and the drain electrode 240 are spaced from each other; and    -   M4: forming the organic semiconductor layer 230 on the        insulating layer 260 to cover and electrically connected to the        source electrode 220 and the drain electrode 240, comprising:        -   M41: providing the evaporating source 110, wherein the            evaporating source 110 comprises the carbon nanotube film            structure 112 and the organic semiconductor material 114,            and the organic semiconductor material 114 is located on the            surface of the carbon nanotube film structure 112; and        -   M42: spacing the evaporating source 110 from the insulating            layer 260, the source electrode 220, and the drain electrode            240, and inputting the electromagnetic signal or the            electrical signal to the carbon nanotube film structure 112            to gasify the organic semiconductor material 114 and form            the organic semiconductor layer 230 on the surface of the            insulating layer 260, the surface of the source electrode            220, and the surface of the drain electrode 240.

In another embodiment, a method for forming the reverse staggeredorganic thin film transistor 200 is provided. The depositing surface inthis method consists of the surface of the insulating layer 260. Themethod for forming the reverse staggered organic thin film transistor200 comprises the following steps:

-   -   P1: forming the gate electrode 250 on the surface the insulating        substrate 210;    -   P2: forming the insulating layer 260 to cover the gate electrode        250;    -   P3: forming the organic semiconductor layer 230 on the        insulating layer 260, comprising:        -   P31: providing the evaporating source 110, wherein the            evaporating source 110 comprises the carbon nanotube film            structure 112 and the organic semiconductor material 114,            and the organic semiconductor material 114 is located on the            surface of the carbon nanotube film structure 112; and        -   P32: spacing the evaporating source 110 from the insulating            layer 260, and inputting the electromagnetic signal or the            electrical signal to the carbon nanotube film structure 112            to gasify the organic semiconductor material 114 and form            the organic semiconductor layer 230 on the surface of the            insulating layer 260; and    -   P4: forming the source electrode 220 and the drain electrode 240        on the organic semiconductor layer 230, wherein the source        electrode 220 and the drain electrode 240 are spaced from each        other and electrically connected to the organic semiconductor        layer 230.

Referring to FIG. 2, one embodiment provides an apparatus 100 forforming the organic thin film transistor 200. The apparatus 100comprises an evaporating source 110 and a heating device. Theevaporating source 110 comprises a carbon nanotube film structure 112and an organic semiconductor material 114. The carbon nanotube filmstructure 112 is a carrying structure for the organic semiconductormaterial 114. The organic semiconductor material 114 is located on asurface of the carbon nanotube film structure 112. The heating device isconfigured to input an electromagnetic signal or an electrical signal tothe carbon nanotube film structure 112 to evaporate the organicsemiconductor material 114. In one embodiment, the heating device caninput the electromagnetic signal to the carbon nanotube film structure112 by an electromagnetic signal input device 140. In anotherembodiment, the heating device can input the electrical signal to thecarbon nanotube film structure 112 by a first electrical signal inputelectrode 150 and a second electrical signal input electrode 152.

The apparatus 100 may further comprise a vacuum room 130. In oneembodiment, the evaporating source 110 and an insulating substrate 210are located in the vacuum room 130. The insulating substrate 210 isspaced from the evaporating source 110.

The apparatus 100 may further comprise two supporters 120. The twosupporters 120 are spaced from each other and disposed on two ends ofthe carbon nanotube film structure 112. The carbon nanotube filmstructure 112 is suspended by the two supporters 120.

The apparatus 100 may further comprise a patterned grid 160. In oneembodiment, the patterned grid 600 is located between the evaporatingsource 110 and a surface of the insulating substrate 210.

The carbon nanotube film is free-standing structure and used to carry anorganic semiconductor material. The carbon nanotube film has a largespecific surface area and good uniformity so that the organicsemiconductor material carried by the carbon nanotube film can uniformlydistributed on the carbon nanotube film before evaporation. The carbonnanotube film can be heated instantaneously. Thus the organicsemiconductor material can be completely gasified in a short time toform a uniform gaseous organic semiconductor material, and the uniformgaseous organic semiconductor material can be uniformly distributed overa large area. The distance between the depositing substrate and thecarbon nanotube film is small. Thus the organic semiconductor materialcarried on the carbon nanotube film can be substantially utilized tosave the organic semiconductor material and improve the deposition rate.

Even though numerous characteristics and advantages of certain inventiveembodiments have been set out in the foregoing description, togetherwith details of the structures and functions of the embodiments, thedisclosure is illustrative only. Changes may be made in detail,especially in matters of arrangement of parts, within the principles ofthe present disclosure to the full extent indicated by the broad generalmeaning of the terms in which the appended claims are expressed.

Depending on the embodiment, certain of the steps of methods describedmay be removed, others may be added, and the sequence of steps may bealtered. It is also to be understood that the description and the claimsdrawn to a method may comprise some indication in reference to certainsteps. However, the indication used is only to be viewed foridentification purposes and not as a suggestion as to an order for thesteps.

The embodiments shown and described above are only examples. Even thoughnumerous characteristics and advantages of the present technology havebeen set forth in the foregoing description, together with details ofthe structure and function of the present disclosure, the disclosure isillustrative only, and changes may be made in the detail, especially inmatters of shape, size and arrangement of the parts within theprinciples of the present disclosure up to, and including the fullextent established by the broad general meaning of the terms used in theclaims. It will, therefore, be appreciated that the embodimentsdescribed above may be modified within the scope of the claims.

What is claimed is:
 1. A method for forming an organic thin filmtransistor comprising: S1: providing an insulating substrate; S2:applying an organic semiconductor layer on the insulating substrate,wherein a method for forming the organic semiconductor layer comprisesthe following steps: S21: providing an evaporating source, wherein theevaporating source consists of a carbon nanotube film structure and anorganic semiconductor material, and the organic semiconductor materialis located on a carbon nanotube film structure surface; and S22: spacingthe evaporating source from the insulating substrate, and heating thecarbon nanotube film structure to gasify the organic semiconductormaterial and form the organic semiconductor layer on a depositingsurface; S3: obtaining a source electrode and a drain electrode spacedfrom each other and separately electrically connected to the organicsemiconductor layer; and S4: forming a gate electrode and an insulatinglayer, wherein the gate electrode is insulated from the organicsemiconductor layer via the insulating layer; wherein the organicsemiconductor material is disposed on the carbon nanotube film structuresurface by a solution method, a vapor deposition method, a platingmethod or a chemical plating method; and wherein the solution method fordisposing the organic semiconductor material on the carbon nanotube filmstructure surface comprising: S11, dispersing an organic semiconductormaterial in a solvent to form a mixture; S12, attaching the mixture tothe carbon nanotube film structure; S13, drying the solvent to make theorganic semiconductor material uniformly attach on the carbon nanotubefilm structure surface.
 2. The method of claim 1, wherein the organicsemiconductor material comprises a plurality of materials, and theplurality of materials are dissolved in a liquid phase solvent and mixedwith each other.
 3. The method of claim 1, wherein in the S2, theevaporating source and the organic semiconductor material are located ina vacuum room.
 4. The method of claim 1, wherein an electromagneticsignal is inputted to heat the carbon nanotube film structure by anelectromagnetic signal input device.
 5. The method of claim 1, whereinan electrical signal is inputted to heat the carbon nanotube filmstructure by a first electrical signal input electrode and a secondelectrical signal input electrode.
 6. The method of claim 1, wherein theS2 further comprises a step of providing a patterned grid and locatingthe patterned grid between the evaporating source and the depositingsurface to form a patterned organic semiconductor layer.
 7. The methodof claim 6, wherein the patterned grid comprises an array of throughholes, and an array of organic semiconductor layers is formed by thearray of through holes.
 8. The method of claim 1, wherein a distancebetween the depositing surface and the carbon nanotube film structure isin a range from about 1 micrometer to about 10 millimeters.
 9. Themethod of claim 1, wherein the depositing surface is an insulatingsubstrate surface or an insulating layer surface.
 10. The method ofclaim 1, wherein a heat capacity per unit area of the carbon nanotubefilm structure is less than 2×10⁻⁴ J/cm²·K, and a specific surface areaof the carbon nanotube film structure is larger than 200 m²/g.
 11. Themethod of claim 1, wherein the carbon nanotube film structure comprisesat least one carbon nanotube film, the least one carbon nanotube filmcomprises a plurality of nanotubes joined end to end by Van der Waalsattractive force.
 12. A method for forming an organic thin filmtransistor comprising: S1: forming an organic semiconductor layer on aninsulating substrate, comprising: S11: providing an evaporating source,wherein the evaporating source consists of a carbon nanotube filmstructure and an organic semiconductor material, and the organicsemiconductor material is located on a carbon nanotube film structuresurface; and S12: spacing the evaporating source from the insulatingsubstrate, and heating the carbon nanotube film structure to gasify theorganic semiconductor material and form the organic semiconductor layeron the insulating substrate; S2: forming a source electrode and a drainelectrode on the organic semiconductor layer, wherein the sourceelectrode and the drain electrode are spaced from each other andelectrically connected to the organic semiconductor layer; S3: formingan insulating layer to cover the source electrode, the drain electrode,and the organic semiconductor layer; and S4: forming a gate electrode onthe insulating layer; wherein the organic semiconductor material isdisposed on the carbon nanotube film structure surface by a solutionmethod, a vapor deposition method, a plating method or a chemicalplating method; and wherein the solution method for disposing theorganic semiconductor material on the carbon nanotube film structuresurface comprising: S11, dispersing an organic semiconductor material ina solvent to form a mixture; S12, attaching the mixture to the carbonnanotube film structure; S13, drying the solvent to make the organicsemiconductor material uniformly attach on the carbon nanotube filmstructure surface.